1. Field of the Invention
The invention relates to the use of soluble, amorphous, conjugated spiro-linked oligomers and polymers as materials for nonlinear optics. It furthermore relates to optical beam guides (waveguides) which are made from these compounds or comprise them and exhibit non-linear optical effects, and to non-linear optical structural elements (components) which are based on such beam guides.
2. Description of the Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
The term xe2x80x9cnon-linear opticsxe2x80x9d describes phenomena, and application thereof, which chiefly occur during interaction between high light intensities or high electric field strengths and specific materials. These effects are based on the polarization of matter by an electric field. This can be represented in a power series:
P="khgr"(1)E+"khgr"(2)E2+"khgr"(3)E3+ . . .
The "khgr"(n) are the so-called electric susceptibility functions. E is the electric field and can comprise several frequency components and may therefore be made up of light or a voltage or a combination thereof. The susceptibility is linked to the so-called molecular hyperpolarizability:
"khgr"(2)xcx9cNxcex2; "khgr"(3)xcx9cNxcex3,
in which N is the density of the active molecules and xcex2 and xcex3 represent the hyperpolarizabilities of the 2nd and 3rd order. The susceptibilities usually decrease with increasing potency, and non-linear optical (NLO) effects therefore become visible only at high field strengths. Furthermore, all susceptibilities of an even order are zero if the individual molecules are arranged centrosymmetrically in the material or the molecules themselves show inversion symmetry.
Effects of the 3rd order, which also occur in systems with inversion symmetry, are, for example, the 4-wave mixture in which light rays having three different frequencies form one light ray having a fourth frequency. The degenerate 4-wave mixture in which all 4 rays have the same frequency is of particular interest for applications. This leads to the so-called optical Kerr effect, in which the refractive index of the material depends not only on the wavelength but also on the intensity of the light ray. On the basis of the Kerr effect, real-time holograms can be established, or purely optical circuit elements which could be suitable for use in optical computers can be developed.
For optical circuit elements in particular, it is advantageous and often necessary for the NLO-active materials to be employed as beam guides either in a light-conducting fiber or as a planar waveguide on a substrate. On the one hand, a waveguide arrangement allows the construction of integrated optical structural elements, and on the other hand the waveguide has the effect that the light intensity and therefore the field strength remain high over a longer path and the NLO effects are greater. However, this can only be achieved if the optical losses in the waveguide which occur due to absorption and light scattering are as small as possible. Examples of structural elements based on NLO-active beam guides are opto-optical couplers, Mach-Zehnder interferometers, mode-selective couplers and prism couplers, which can be employed in communications technology or for optical computers. The invention relates to these and other structural elements and applications, which are described, for example, by G. Stegeman et al. in Nonlinear Optical Effects in Organic Polymers, pages 257-276 (Dordrecht: Kluwer, 1989), using conjugated spiro compounds, but is not limited to these structural elements and applications mentioned.
Beam guides can be employed appropriately for applications in non-linear optics only if the optical losses which occur due to absorption and light scattering are as low as possible. An ideal material for use in NLO of the 3rd order should absorb as little as possible at the desired use wavelength, and should also have a homogeneous, preferably an amorphous, structure, in order to prevent light scattering. Furthermore, the material should be readily processible and optically, chemically and thermally stable.
For effects of the 3rd order, conjugated polymers and oligomers, for example poly(phenylenevinylene), poly(diacetylene) or sexi(thiophene), have proven to be interesting materials having relatively high susceptibilities of the 3rd order. Examples of conjugated organic materials for non-linear optics of the 3rd order are described by G. H. Cross in Nonlinear Optical Materials, pages 189-225 (London: Blackie Academic and Professional, 1993) and by D. Neher in Advan. Mater., 7, 8, pages 691-702 (1995). The substances available to date cannot fulfill all the above-mentioned conditions at the same time. Many of the compounds, for example poly(thiophenes), poly(anilines) or poly(phenylenevinylenes), are intensely colored and are therefore unsuitable for waveguides in the visible range. Poly(arylenevinylenes) furthermore are often sensitive to oxygen and light. Conjugated polymers and oligomers moreover are usually insoluble or poorly soluble, and are therefore difficult to process from solution using typical coating processes, and often form polycrystalline, light-scattering layers. This applies in particular to colorless compounds such as, for example, poly(phenylenes). However, the method frequently used of increasing the solubility and suppressing crystallization with long-chain substituents is accompanied by a dilution of the active units and a reduction in NLO susceptibility. Furthermore, the mechanical stability of the films is impaired as a result.
It is an object of the present invention to develop a method of using a spiro compound as materials for non-linear optics which improves the solubility, stability, achives good non-linearly optical activity, low optical losses and avoids the disadvantages of problems mentioned.
It is also an object of the present invention to provide a non-linearly optical structural element, which comprises or consists of a monomeric or polymeric spiro compound as described above. Preferably, non-linearly optical effects of the third order are exploited in this structural element.
It is yet an object of the present invention to provide a non-linearly optical structural element, which comprises an optical waveguide comprising or consisting of a monomeric or polymeric spiro compound as described above. Preferably this non-linearly optical structural element is an opto-optical coupler, a Mach-Zehnder interferometer, a mode selective coupler or a prism coupler.
It has been found, surprisingly, that the monomeric and polymeric spiro and heterospiro compounds described below are particularly suitable as materials for non-linear optics, since they do not have the above-mentioned disadvantages because they are soluble, stable and amorphous substances and at the same time have a good non-linearly optical activity and low optical losses. In the context of this application the term xe2x80x9cspiro compoundxe2x80x9d includes monomeric and polymeric carbo spiro and hetero spiro compounds.
Accordingly, an aspect of the invention relates to the use of spiro compounds of the formula (I), 
in which "psgr" is C, Si, Ge or Sn, preferably C, Si or Ge, more preferably C or Si, and in particular C, and K1 and K2 independently of one another are conjugated systems, as materials in non-linear optics.
Spirocompounds are compounds in which two ring systems are linked by a single tetravalent atom. This atom is referred to as a spiro atom, as explained in Handbook of Chemistry and Physics, 62nd edition (1981-2), CRC Press, pages C-23 to C-25.
Preferred compounds of the formula (I) are 9,9xe2x80x2-spirobifluorene derivatives of the formula (II), 
in which "psgr" has the above-mentioned meanings, and in which the benzo groups can be substituted and/or fused independently of one another.
Particularly preferred compounds are spirobifluorene derivatives of the formula (III), 
in which the symbols and indices have the following meanings:
"psgr" is C, Si, Ge or Sn, preferably C, Si or Ge, particularly preferably C or Si, in particular C,
K, L, M and N are identical or different and are a group of the formulae 
R has the same meaning, identical or different, as K, L, M and N, or is hydrogen, a linear or branched alkyl, alkoxy, sulfide, sulfonyl or carboalkoxy group having 1 to 22, preferably 1 to 15, particularly preferably 1 to 12, carbon atoms, xe2x80x94CN, xe2x80x94NO2, halogen, xe2x80x94NR1R2, xe2x80x94Ar or xe2x80x94Oxe2x80x94Ar;
Ar is phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 2-thienyl or 2-furanyl, where each of these groups can carry one or two radicals R;
m, n and p are 0, 1, 2or 3;
X and Y are xe2x95x90CRxe2x80x94 or xe2x95x90Nxe2x80x94;
Z is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NRxe2x80x94, xe2x80x94CRRxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94CHxe2x95x90Nxe2x80x94; and
R1 and R2 are hydrogen, a linear or branched alkyl group having 1 to 22 C atoms, xe2x80x94Ar or 3-methylphenyl.
Preferred compounds of the formula (III) are those of the formulae (IIIa)-(IIIg) xe2x80x83xe2x80x83IIIa) K=L=M=N and is a group of the formulae: 
R=C1-C22-alkyl or C2H4SO3xe2x88x92
IIIb) K=M=H and Nxe2x95x90L and is a group of the formulae: 
IIIC, K=M and is a group of the formulae: 
and Nxe2x95x90L and is a group of the formulae: 
IIId) K=M and is a group of the formulae: 
and Nxe2x95x90L and is a group of the formulae: 
IIIe) K=L=H and M=N and is a group of the formulae: 
IIIf) K=L and is a group of the formulae: 
and M=N and is a group of the formulae: 
IIIg) K=L and is a group of the formulae: 
and M=N and is a group of the formulae: 
Particularly preferred compounds of the formula (III) are those of the formulae (IIIaa) to (IIIdb):
(IIIaa) K=L=M=N and is a group of the formulae: 
(IIIba) K=M=H and Nxe2x95x90L and is a group of the formulae: 
(IIIca) K=M and is a group of the formulae: 
and Nxe2x95x90L and is: 
(IIIda) K=M and is a group of the formulae: 
and Nxe2x95x90L and is: 
(IIIab) K=L=M=N and is a group of the formulae: 
(IIIbb) K=L=H and M=N and is a group of the formulae: 
(IIIcb) K=L and is a group of the formulae: 
and M=N and is: 
(IIIdb) K=L and is a group of the formulae: 
Especially preferred spiro compounds are those of the formula (IV), 
in which the symbols have the following meanings:
"psgr" is C or Si, preferably C;
K, L, M and N are identical or different and are one of the groups G1 to G14: 
and R5 and R6 are, identical or different, hydrogen, a linear or branched alkyl, alkyloxy or ester group having 1 to 22 C atoms, xe2x80x94CN or xe2x80x94NO2.
Particularly preferred Spiro compounds of the formula (IV) are
2,2xe2x80x2,4,4xe2x80x2,7,7xe2x80x2-hexakis(biphenylyl)-9,9xe2x80x2-spirobifluorene,
2,2xe2x80x2,4,4xe2x80x2,7,7xe2x80x2-hexakis(terphenylyl)-9,9xe2x80x2-spirobifluorene,
2,2xe2x80x2,4,4xe2x80x2-hexakis(biphenylyl)-9,9xe2x80x2-spirobi-9-silafluorene and
2,2xe2x80x2,4,4xe2x80x2,7,7xe2x80x2-hexakis(terphenylyl)-9,9xe2x80x2-spirobi-9-silafluorene.
The spiro and heterospiro compounds used according to the invention are prepared by methods known per se, such as are described in EP-A-0 676 461 and in standard works on organic synthesis, for example Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart and in the corresponding volumes of the series The Chemistry of Heterocyclic Compounds, A. Weissberger and E. C. Taylor (editors).
The preparation is carried out here under reaction conditions which are known and suitable for the reactions mentioned. It is also possible to use in these reactions variants which are known per se but are not mentioned here in more detail.
a) Spiro Compounds
Compounds of the formula (III) are obtained, for example, from 9,9xe2x80x2-spirobifluorene, the synthesis of which is described, for example, by R. G. Clarkson, M. Gomberg, J. Am. Chem. Soc., 1930, 52, 2881.
Compounds of the formula (IIIa) can be prepared, for example, starting from a tetrahalogenation in positions 2,2xe2x80x2,7,7xe2x80x2 of 9,9xe2x80x2-spirobifluorene and a subsequent substitution reaction (cf., for example, U.S. Pat. No. 5,026,894), or via tetraacetylation of positions 2,2xe2x80x2,7,7xe2x80x2 of 9,9xe2x80x2-spirobifluorene with subsequent Cxe2x80x94C linking after conversion of the acetyl groups into aldehyde groups, or build-up of heterocyclic radicals after conversion of the acetyl groups into carboxylic acid groups.
Compounds of the formula (IIIb) can be prepared, for example, analogously to those of the formula IIIa, the stoichiometric ratios in the reaction being chosen such that positions 2,2xe2x80x2 and 7,7xe2x80x2 are functionalized (cf., for example, J. H. Weisburger, E. K. Weisburger, F. E. Ray, J. Am. Chem. Soc., 1959, 72, 4253; F. K. Sutcliffe, H. M. Shahidi, D. Paterson, J. Soc. Dyers Colour, 1978, 94, 306 and G. Haas, V. Prelog, Helv. Chim. Acta, 1969, 52, 1202).
Compounds of the formula (IIIc) can be prepared, for example, via dibromination in the 2,2xe2x80x2-position and subsequent diacetylation in the 7,7xe2x80x2 position of 9,9xe2x80x2-spirobifluorene, and subsequent reaction analogously to that of the compounds (IIIa).
Compounds of the formulae (IIIe)-(IIIg) can be prepared, for example, by choosing suitably substituted starting compounds when building up the spirobifluorene, for example 2,7-dibromospirobifluorene can be built up from 2,7-dibromofluorenone and 2,7-dicarbethoxy-9,9-spirobifluorene can be built up by using 2,7-dicarbethoxyfluorenone. The free 2xe2x80x2,7xe2x80x2-positions of the spirobifluorene can then be further substituted independently.
For synthesis of the groups K, L, M and N, reference may be made, for example, to DE-A 23 44 732, 24 50 088, 24 29 093, 25 02 904, 26 36 684, 27 01 591 and 27 52 975 for compounds with 1,4-phenylene groups; DE-A 26 41 724 for compounds with pyrimidine-2,5-diyl groups; DE-A 40 26 223 and EP-A 03 91 203 for compounds with pyridine-2,5-diyl groups; DE-A 32 31 462 for compounds with pyridazine-3,6-diyl groups; and N. Miyaura, T. Yanagi and A. Suzuki, Synthetic Communications, 1981, 11, 513 to 519; DE-A 39 30 663,; M. J. Sharp, W. Cheng, V. Snieckus, Tetrahedron Letters, 1987, 28, 5093; G. W. Gray, J. Chem. Soc. Perkin Trans II, 1989, 2041 and Mol. Cryst. Liq. Cryst., 1989, 172, 165; Mol. Cryst. Liq. Cryst., 1991, 204, 43 and 91; EP-A 0 449 015; WO 89/12039; WO 89/03821; and EP-A 0 354 434 for direct linkage of aromatics and heteroaromatics.
The preparation of disubstituted pyridines, disubstituted pyrazines, disubstituted pyrimidines and disubstituted pyridazines is to be found, for example, in the corresponding volumes of the series The Chemistry of Heterocyclic Compounds, A. Weissberger and E. C. Taylor (editors).
b) Heterospiro Compounds
Such compounds of the formula (III) are obtained, for example, starting from bis[biphenyl-2,2xe2x80x2-diyl]silane(=9,9xe2x80x2-spirobi(9H-)-silafluorene) (V), the synthesis of which is described, for example, by H. Gilman, R. D. Gorsich, J. Am. Chem. Soc., 1958, 80, 3243. 
The heterospiro compounds of the formula (IIIa) can be prepared, for example, starting from a tetrahalogenation in positions 2,2xe2x80x2,7,7xe2x80x2 of 9,9xe2x80x2-spirobi-9-silafluorene and a subsequent substitution reaction, which is known for analogous C-spiro compounds (cf., for example, U.S. Pat. No. 5,026,894), or via tetraacetylation of positions 2,2xe2x80x2,7,7xe2x80x2 of 9,9xe2x80x2-spirobi-9-silafluorene with subsequent Cxe2x80x94C-linkage after conversion of the acetyl groups into aldehyde groups or build-up of the heterocyclic radical after conversion of the acetyl groups into carboxylic acid groups.
Compounds of the formula (IIIb) can be prepared, for example, analogously to those of the formula (IIIa), the stoichiometric ratios in the reaction being chosen such that positions 2,2xe2x80x2 and 7,7xe2x80x2 are functionalized (cf., for example, J. H. Weisburger, E. K. Weisburger, F. E. Ray, J. Am. Chem. Soc., 1959, 72, 4253; F. K. Sutcliffe, H. M. Shahidi, D. Paterson, J. Soc. Dyers Colour, 1978, 94, 306 and G. Haas, V. Prelog, Helv. Chim. Acta, 1969, 52, 1202).
Compounds of the formula (IIIc) can be prepared, for example, via dibromination in the 2,2xe2x80x2-position with subsequent diacetylation in the 7,7xe2x80x2-position of 9,9xe2x80x2-spirobi-9-silafluorene and subsequent reaction analogously to that of the compounds (IIIa).
Compounds of the formulae (IIIe)-(IIIg) can be prepared, for example, by choosing suitably substituted starting compounds in building up the spirosilabifluorene in accordance with the following two equations: 
Furthermore, the synthesis sequences with which the expert is familiar, such as nitration, reduction, diazotization and the Sandmeyer reaction, can also be employed. Reference is made to the corresponding C-spiro compounds for synthesis of the groups K, L, M and Q.
A further aspect of the invention is the use of conjugated polymers, comprising repeating units of the formula (VI), as materials in non-linear optics, 
wherein the symbols and indices in formula (VI) have the following meanings:
"psgr" is Sn, Ge, Si or C, particularly preferably C or Si, especially preferably C;
D, E, F and G are identical or different and are xe2x80x94CR1R2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR3xe2x80x94 or a chemical bond; in which R1, R2 and R3 are C1-C20-alkyl or H, and in which R1 and R2 together can form an optionally substituted cycloalkyl ring;
U is xe2x80x94CR4xe2x95x90CR5xe2x80x94 or a chemical bond;
V has the meaning of U or is xe2x80x94CR1R2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR3xe2x80x94, xe2x80x94SiR1R2xe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94SOxe2x80x94 or xe2x80x94COxe2x80x94, in which R1, R2 and R3 have the above-mentioned meaning and R4 and R5 have the meaning of R1, R2 and R3 or are fluorine or CF3;
A is hydrogen, C1-C20-, preferably C1-C15-alkyl, which can also contain heteroatoms, such as xe2x80x94Oxe2x80x94, xe2x80x94N or fluorine, particularly preferably a linear, branched or ring-containing alkyl, alkoxy or alkyloxycarbonyl group, xe2x80x94CF3, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR6R7, xe2x80x94Ar or xe2x80x94Oxe2x80x94Ar;
R6 and R7 are hydrogen or a C1-C20-hydrocarbon radical, which can be aliphatic, aromatic, linear, branched or alicyclic, in which R6 together with R7 can form a ring,
R6 and R7 are preferably methyl, ethyl, t-butyl, cyclohexyl, 3-methylphenyl or, together, 
Ar is an aromatic radical having up to 22 carbon atoms, preferably phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 2-thienyl or 2-furanyl, where each of these groups Ar can carry one or two radicals having the meaning of A;
T is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR3xe2x80x94, xe2x80x94CR1R2xe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94CAxe2x95x90CAxe2x80x94, xe2x80x94CHxe2x95x90CAxe2x80x94, xe2x80x94CHxe2x95x90CFxe2x80x94 or xe2x80x94CFxe2x95x90CFxe2x80x94, in which R1, R2, R3 and A have the above-mentioned meaning, T is preferably xe2x80x94CHxe2x95x90CHxe2x80x94; and
K, L, M and Q are identical or different hydrocarbon radicals which contain conjugated electron systems and can contain heteroatoms, where K, L, M and Q, with the particular groups A in the ortho-position, can also be closed together to form a ring, which is saturated, partly unsaturated or unsaturated to the maximum degree, a fused aromatic ring system preferably being present in those cases, L, M can also be H, a non-conjugated hydrocarbon radical, preferably containing 1 to 20 carbon atoms, which can contain hetero atoms, halogen, CN, NO2, an amino, alkylamino or dialkylamino group.
Preferred polymers are conjugated polymers comprising repeating units of the formula (VII), 
in which the symbols and indices have the following meaning:
"psgr" is Sn, Ge, Si or C;
Q, K, L and M are identical or different, in each case one to fifteen identical or different arylene and/or heteroarylene and/or vinylene groups, which can optionally be substituted, L, M can also be H, a non-conjugated hydrocarbon radical, preferably containing 1 to 20 carbon atoms, which can contain hetero atoms, halogen, CN, NO2, an amino, alkylamino or dialkylamino group;
A is as defined for formula VI; and
m and n are 0 or 1.
The polymers of the formula (VI) and (VII) in general have 2 to 1000, preferably 2 to 500, particularly preferably 2 to 100, recurring units.
Preferred polymers are furthermore those in which the symbols and indices in the formula (VII) have the following meanings:
A is identical or different and is R1, R2, R3 and/or R4;
Q and K are identical or different and are conjugated C2 to C100 hydrocarbon radicals, in particular groups of the formulae 
X, Y, B and D are identical or different and are CR5 or N;
Z and W are identical or different and are xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR5xe2x80x94, xe2x80x94CR5R6xe2x80x94, xe2x80x94CR5xe2x95x90CR6xe2x80x94 or xe2x80x94CR5xe2x95x90Nxe2x80x94;
p, q and r are identical or different and are 0 or 1 to 5;
R1, R2, R3, R4, R5, R6, R7 and R8 are identical or different and are H, a straight-chain or branched alkyl, alkoxy or ester group having 1 to 22 carbon atoms, aryl and/or aryloxy groups, preferably phenyl and/or phenyloxy groups, in which the aromatic can be substituted by C1-C22-alkyl, C1-C22-alkoxy, Br, Cl, F, CN and/or NO2, or Br, Cl, F, CN, NO2 or CF3;
L and M are identical or different and are H or, preferably, groups of the formulae 
R9 is identical or different and is H, an unbranched or branched alkyl or alkoxy group having 1 to 22 carbon atoms, xe2x80x94CN, xe2x80x94NO2, xe2x80x94NR11R12, phenyl, biphenyl, 1-naphthyl, 2-naphthyl, 2- thienyl and 2-furanyl, where the aryls and heteroaryls can carry a further substituent R9;
X and Y are identical or different and are xe2x95x90CR5xe2x80x94 or xe2x95x90Nxe2x80x94;
Z is identical or different and is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NR11xe2x80x94, CR5R6, xe2x80x94CR5xe2x95x90CR6xe2x80x94 or xe2x80x94CR5xe2x95x90Nxe2x80x94; and
R11 and R12 are identical or different and are H, an unbranched or branched alkyl group having 1 to 22 carbon atoms, phenyl, 3-methylphenyl, biphenyl, 1-naphthyl or 2-naphthyl;
s, t, u are identical or different 0, 1, 2, 3, 4 or 5.
Particularly preferred polymers, comprising repeating units of the formula (VII), are those in which:
Q and K are a group of the following formulae 
m and n are identical or different and are 0 or 1;
L and M are identical or different and are H or, preferably, a group of the formulae 
R=alkyl or C2H4SO3xe2x80x94
Especially preferred compounds of the formula (VII) are the following, in which:
Q and K are identical or different and in each case are a group of the formulae 
m+n is 0 or 1; and
L and M are identical or different and in each case are H or, preferably, a group of the formulae 
For some applications, it may be advantageous to replace one, several or all the hydrogen atons, preferably aromatic hydrogen atoms, by F atoms.
The polymers, comprising repeating units of the formulae (VI) and (VII), are homo- or copolymers, i.e. they can also contain different repeating units of the type mentioned. This type of spiro compound can be prepared, for example, by the following route:
Starting compounds which are employed for the preparation of these polymers are in general monomers having a 9,9xe2x80x2-spirobifluorene center which are substituted in the 2,7- and optionally 2xe2x80x2,7xe2x80x2-position.
Methods for the synthesis of the monomers are based, for example, on the synthesis of 9,9xe2x80x2-spirobifluorene, for example from 2-bromobiphenyl and fluorenone via a Grignard synthesis, such as described by R. G. Clarkson, M. Gomberg, J. Am. Chem. Soc., 1930, 52, 2881, the product subsequently being further substituted in a suitable manner.
Functionalizations of 9,9xe2x80x2-spirobifluorene are described, for example, in J. H. Weisburger, E. K. Weisburger, F. E. Ray, J. Am. Chem. Soc., 1959, 72, 4253; F. K. Sutcliffe, H. M. Shahidi, D. Paterson, J. Soc. Dyers Colour, 1978, 94, 306; and G. Haas, V. Prelog, Helv. Chim. Acta, 1969, 52, 1202.
The desired substitution pattern of the 9,9xe2x80x2-spirobifluorene monomer is obtained in a considerably more favorable manner if the spiro linkage already takes place starting from suitably substituted educts, for example with 2,7-difunctionalized fluorenones, and the still free 2xe2x80x2,7xe2x80x2-positions are then optionally further functionalized (for example by halogenation or acylation, with subsequent Cxe2x80x94C linkage after conversion of the acetyl groups into aldehyde groups, or by build-up of the heterocyclic radical after conversion of the acetyl groups into carboxylic acid groups) after the spiro center has been built up.
Further functionalization can be carried out by methods known per se from the literature, such as are described in standard works on organic synthesis, for example Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme Verlag, Stuttgart and in the corresponding volumes of the series The Chemistry of Heterocyclic Compounds, A. Weissberger and E. C. Taylor (editors).
For synthesis of the groups A, B, C and D, reference may be made, for example, to DE-A 23 44 732, 24 50 088, 24 29 093, 25 02 904, 26 36 684, 27 01 591 and 27 52 975 for compounds with 1,4-phenylene groups; DE-A 26 41 724 for compounds with pyrimidine-2,5-diyl groups; DE-A 40 26 223 and EP-A 03 91 203 for compounds with pyridine-2,5-diyl groups; DE-A 32 31 462 for compounds with pyridazine-3,6-diyl groups; and N. Miyaura, T. Yanagi and A. Suzuki in Synthetic Communications, 1981, 11, 513 to 519, DE-A 39 30 663, M. J. Sharp, W. Cheng, V. Snieckus, Tetrahedron Letters, 1987, 28, 5093; G. W. Gray, J. Chem. Soc. Perkin Trans., II 1989, 2041 and Mol. Cryst. Liq. Cryst., 1989, 172, 165; Mol. Cryst. Liq. Cryst., 1991, 204, 43 and 91; EP-A 0 449 015; WO 89/12039; WO 89/03821; and EP-A 0 354 434 for direct linkage of aromatics and heteroaromatics.
The preparation of disubstituted pyridines, disubstituted pyrazines, disubstituted pyrimidines and disubstituted pyridazines is to be found, for example, in the corresponding volumes of the series The Chemistry of Heterocyclic Compounds, A. Weissberger and E. C. Taylor (editors).
Starting from the above-mentioned monomers, polymerization to give the polymers according to the invention is possible by several methods.
For example, derivatives of 9,9xe2x80x2-spirobifluorene can be polymerized oxidatively (for example with FeCl3, cf., inter alia, P. Kovacic, N. B. Jones, Chem. Ber., 1987, 87, 357 to 379; and M. Weda, T. Abe, H. Awano, Macromolecules, 1992, 25, 5125) or electrochemically (cf., for example, N. Saito, T. Kanbara, T. Sato, T. Yamamoto, Polym. Bull., 1993, 30, 285).
The polymers according to the invention can likewise be prepared from 2,7-difunctionalized 9,9xe2x80x2-spirobifluorene derivatives.
Dihaloaromatics can be polymerized under copper/triphenylphosphane (cf., for example, G. W. Ebert, R. D. Rieke, J. Org. Chem., 1988, 53, 4482) or nickel/triphenylphosphane catalysis (cf., for example, H. Matsumoto, S. Inaba, R. D. Rieke, J. Org. Chem., 1983, 48, 840).
Aromatic diboron acids and aromatic dihalides or mixed aromatic halogen-boron acids can be polymerized by coupling reactions under palladium catalysis (cf., for example, M. Miyaura, T. Yanagi, A. Suzuki, Synth. Commun., 1981, 11, 513; and R. B. Miller, S. Dugar, Organometallics, 1984, 3, 1261).
Aromatic distannanes can be polymerized under palladium catalysis, for example as described by J. K. Stille, Angew. Chem. Int., English edition 1986, 25, 508.
Furthermore, the above-mentioned dibromine compounds can be converted into the dilithio or di-Grignard compounds, which are then polymerized with further dibromine compound by means of CuCl2 (Cf., for example, G. Wittig, G. Klar, Liebigs Ann. Chem., 1967, 704, 91; H. A. Stabb, F. Bunny, Chem. Ber., 1967, 100, 293; and T. Kaufmann, Angew. Chem., 1974, 86, 321 to 354) or by electron transfer of unsaturated 1,4-dihalogen compounds (cf., for example, S. K. Taylor, S. G. Bennett, K. J. Harz, L. K. Lashley, J. Org. Chem., 1981, 46, 2190).
However, the polymers, comprising repeating units of the formula (VI), can also be synthesized by polymerization of a 2,7-difunctionalized 9,9xe2x80x2-spirobifluorene derivative with another suitably difunctionalized compound.
Thus, for example, 2,7-dibromo-9,9xe2x80x2-spirobifluorene can be polymerized with 4,4xe2x80x2-biphenylylbis-boron acid. In this manner, at the same time as the polymerization step, the build-up of various heterocyclic units is possible, such as, for example, the formation of oxadiazole units from difunctional carboxylic acid halides and difunctional carboxylic acid hydrazides, or from the corresponding dicarboxylic acid and hydrazine sulfate (B. Schulz, E. Leibnitz, Acta Polymer, 1992, 43, 343; and JP 05/178,990 [93,178,990]), or alternatively from dicarboxylic acid halides and bistetrazoles (C. A. Abshire, C. S. Marvel, Makromol. Chem., 1961, 44 to 46, 388).
To prepare copolymers, for example, different monomers, comprising structural units of the formula (VI) or (VII) can be polymerized together.
Working up is carried out by known methods with which the expert is familiar, such as are described, for example, by D. Braun, H. Cherdron, W. Kern, Praktikum der makromolekularen organischen Chemie [Practical Macromolecular Organic Chemistry], 3rd edition, Huthig Verlag, Heidelberg, 1979, page 87 et seq. For example, the reaction mixture can be filtered, diluted with aqueous acid and extracted and the crude product obtained after drying and stripping off the solvent can be further purified by reprecipitation.
Terminal bromine atoms can be removed reductively, for example with LiAlH4 (cf., for example, J. March, Advanced Organic Chemistry., 3rd edition. McGraw-Hill, page 510).
The synthesis of the described polymers is also described in EP-A 0 707 020; WO-A 96/17036; DE-A 196 06 511; DE-A 196 14 971 and DE-A 196 15 128.
On the basis of the above-mentioned properties of these spiro compounds, such as solubility, stability and amorphous structures, with a simultaneous good non-linear optical activity and low optical losses, the spiro compounds described above are especially suitable as a material in non-linear optics. They are especially suitable for the exploitation of third order non-linearly optical effects.
Therefore, according to a further aspect of the present invention there is provided a non-linearly optical structural element, which comprises or consists of a monomeric or polymeric spiro compound as described above. Preferably, non-linearly optical effects of the third order are exploited in this structural element.
According to a further aspect of the present invention there is provided a non linearly optical structural element, which comprises an optical waveguide comprising or consisting of a monomeric or polymeric spiro compound as described above. Preferably this non-linearly optical structural element is an opto-optical coupler, a Mach-Zehnder interferometer, a mode selective coupler or a prism coupler.